System and method for optical bypass routing and switching

ABSTRACT

Optical bypass circuits are selected and created with a desired amount of traffic on each circuit to offload from the IP routers, the maximum possible amount of traffic. In a first phase, each node in a network independently determines the maximum number of optical bypass circuits, configured to their maximum capacity, to as many destinations, that could possibly originate at that node. The determination is made by aggregating traffic from a given traffic matrix. The optical bypass circuit transports traffic that originates at the node plus transient traffic that the node receives from other nodes. In the second phase, the node will eliminate an optical bypass circuit found in the first phase if any of its parent nodes created a necessarily longer optical bypass circuit to the same destination. In addition, if a descendent node has more aggregate traffic to fill more bypass circuits than the parent node, then the extra optical bypass circuits from the descendent node are also created.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing date of U.S.Provisional Application No. 61/254,778, filed on Oct. 26, 2009, thedisclosures of which are incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Funding for research was made with Government support underHR011-09-C-0024 awarded by the Defense Advanced Research Projects Agency(DARPA). The Government has certain rights to this invention.

BACKGROUND

1. Field of the Invention

The present invention relates generally to the field of communicationnetworks, and more particularly to the design of optical bypass routingand switching in communication networks.

2. Description of the Related Art

The increasing popularity of the Internet has increased traffic demandson the backbone networks supporting the Internet. The enormous growth ofthe data traffic on the backbone networks stresses the transmissionbandwidth and burdens the processing capability of the electronicrouters, switches, and multiplexers used in the backbone network.Optical technology has been seen as a promising solution to overcomethis electronic bottleneck. For example, the use of Wavelength DivisionMultiplexing in optical fiber channels has the capability of increasingtransmission rates to 100 Gigabits/second per wavelength. However, thisincreased transmission rate will burden the existing electronic routersand switches used in nodes of the network. Optical bypass has beenconsidered as a method to offload traffic from the electronic routers.This is possible since it is not necessary for a node to process all thetraffic that passes through it destined for other nodes. Although theemergence of optical bypass techniques appears to be a promisingsolution, there are challenges in incorporating these techniques in anIP network.

BRIEF SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described in the Detailed Descriptionbelow. This Summary is not intended to identify essential features ofthe invention or claimed subject matter, nor is it intended to be usedin determining the scope of the claimed subject matter.

The present invention pertains to systems and methods for allocatingoptical bypass circuits in a network. In an embodiment, the system is anarbitrary mesh IP network having fixed routing and general trafficpatterns. The optical bypass circuits are selected and created with aspecified amount of traffic on each circuit to offload from the IProuters, the maximum possible amount of traffic. Optical bypass modules,including components such as optical cross connects, are placed next toIP routers to achieve the bypass capability.

The method is achieved in two phases. In the first phase, each nodeindependently determines the maximum number of optical bypass circuits,each configured to carry a specified amount of traffic, to as manydestinations, not necessarily final destination nodes of the trafficdemand, that could possibly originate at that node. Each optical bypasscircuit has some specified bandwidth, such as a high percentage of awavelength's full capacity. The optical bypass circuit transportstraffic that originates at the node plus transient traffic that the nodereceives from other nodes. In other words, all traffic is considered,such as the traffic originating and passing through a node. In thesecond phase, each node will eliminate an optical bypass circuit foundin the first phase if any of its parent nodes, according to the networkrouting tree, found a necessarily longer optical bypass circuit to thesame, not necessarily final, destination. In addition, if the descendentnode finds in the first phase more bypass circuits than its parentnodes, because the descendent node has more aggregate traffic to thedestination than its parent nodes, then the extra optical bypasscircuits from the descendent node are also created.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter disclosed is illustrated by way of example, and notby way of limitation, in the figures of the accompanying drawings inwhich the like reference numerals refer to similar elements and inwhich:

FIG. 1 is a schematic diagram of an arbitrary mesh network in accordancewith an embodiment;

FIG. 2 is a schematic diagram of an exemplary portion of the networkshown in FIG. 1;

FIG. 3 is a schematic diagram of a portion of the network shown in FIG.2 including optical bypass circuits in accordance with an embodiment;

FIG. 4 is a schematic diagram of an exemplary optical cross connectcircuit;

FIG. 5 is a schematic diagram of a memory element of a networkcontroller in accordance with an embodiment;

FIG. 6 is a schematic diagram illustrating an exemplary routing tree;

FIG. 7 is a flowchart illustrating steps used in the optical bypasscircuit procedure in accordance with an embodiment;

FIG. 8 is a flowchart illustrating steps used in a first phase of theoptical bypass circuit procedure in accordance with an embodiment; and

FIG. 9 is a flowchart illustrating steps used in the second phase of theoptical bypass circuit procedure in accordance with an embodiment.

DETAILED DESCRIPTION

FIG. 1 illustrates an embodiment of a network configuration utilizingthe technology described herein. There is shown an arbitrary meshnetwork 100 composed of a number of nodes, 102, and networks 104,interconnected to each other to facilitate the transmission of datapackets within the network 100. The network 100 can be a core orbackhaul network. The network 100 employs an arbitrary mesh topologywherein each node 102 in the network 100 is connected to one or morenodes 102 in the network 100. The connection between nodes 102 in thenetwork 100 is dynamic and can be reconfigured in the event of broken orblocked paths. Nodes 102 in a mesh network do not require a directconnection between all the other nodes 102, rather the connection can bemade through multiple hops through intermediate nodes.

The nodes 102 can be connected to other networks 104 and can facilitatecommunication between the different networks 104. The nodes areconnected via any type of communication links, such as optical links,wireless links (e.g., radio link, microwave, etc.), wired links, and anycombination thereof. In an embodiment, the network 100 has optical linksin combination with wired communications links (e.g., telecommunicationslinks, etc.). The nodes in the network can be routers, hubs, switches,servers, host computers, other networks (e.g., LANs, WLANs, privatenetworks, etc.), or other network elements.

However, it should be noted that the technology described herein is notconstrained to any particular network configuration, topology, ornetwork components. The technology can be adapted to suit other networkconfigurations and topologies, such as without limitation, ad hocnetworks, MANETs, ring topologies, etc. and in configuration with othernetwork components.

There can be one or more central nodes or central controllers 103 withinthe network 100. The central controllers 103 can be used to superviseand control certain activities within the network 100. Alternatively,the network 100 can utilize a distributed network control mechanismwhere each node contains processes that facilitate the supervisory andcontrol activities within the network.

In an embodiment, the Internet Protocol (“IP”) is used to enablecommunications within the network 100. IP is a packet-switched protocolthat specifies how to segment data into packets with a header thatspecifies a source and a destination. IP is a connectionlesstransmission where a virtual circuit does not need to be establishedbefore the data transfer can begin. The IP layer in each routermaintains a routing table that is used to determine how to handle an IPpacket. The routers work together to route packets from a source to adestination through a series of hops through the network. The IP routingprotocol computes the routing path according to the routing informationthat is maintained in the routing table. The information in the routingtable can be statically configured using static routes or dynamicallyconfigured by exchanging information with other routers in the network.

There are various IP routing protocols that can be used in the network100. One such IP routing protocol is the link state routing protocol. Inthe link state routing protocol, each router stores the entire networktopology and computes the shortest path. When the state of the networkchanges, all nodes are informed by broadcast of update messages to allnodes in the network. However, the technology described herein canutilize any particular IP routing protocol.

FIG. 2 illustrates a schematic diagram of a portion 101 of the network100. FIG. 3 illustrates an optical bypass circuit configuration for thatportion of the network 101. As shown in FIGS. 2 and 3, there is shownseveral nodes 102 a-102 k in the network 101 which are connected toother nodes. Nodes 102 a, 102 h, 102 k contain an optical bypass moduleconsisting in this example of an optical cross connect 106 (“OXC”) whichis used to establish an optical bypass circuit. As shown in FIG. 3,there is an optical bypass circuit that travels from node 102 a to node102 h and another optical bypass circuit that travels from node 102 h tonode 102 k. An optical bypass circuit is used to denote an end-to-endoptical connection that is established between two nodes.

Nodes 102 a, 102 h, 102 k contain a router 108 that can be coupled to anOXC 106. The router 108 is a network device that can route and forwarddata packets, in the form of electrical signals, from one node 102 inthe network 100 to another node, through a communications link 116. Eachrouter 108 can contain a routing table 105 and a traffic matrix 107. Therouting table 105 contains the routes to particular networkdestinations. The routing table 105 lists all reachable destinations andthe addresses of the next node along the path to those destinations.Each packet is transmitted to the next hop until it reaches its finaldestination. At a minimum, the routing table contains at least thedestination node identifier and the next hop or address of the nextrouter to which the packet is to be sent on the way to its finaldestination. The traffic matrix 107 provides for every ingress pointinto a node and every egress point out of the node, the volume oftraffic over a given time interval.

Alternatively, as shown in node 102 h, a node can include a router 108coupled to an OXC 106 through a patch panel X, 112. The node 102 h canalso include an optical data router (“ODR”) 110, which is coupled to theOXC 106 through the patch panel X, 112.

The optical cross connect (“OXC”) 106 is an optical networking devicethat can switch optical signals coming in on a wavelength of an inputfiber link to the same wavelength in an output fiber link. An opticalcommunication channel is the optical transport mechanism and is commonlyreferred to as a lightpath or wavelength channel denoted as λ-channel.The optical bypass circuit is established over a network of OXCs, whichmay span a number of fiber links or physical hops.

FIG. 4 is a more detailed diagram of an exemplary OXC 106. The OXC 106is coupled to a fiber link 114 that is composed of several wavelengths,λ₁, λ₂, . . . , λ_(n). A demultiplexer 140 is used to select onewavelength from the fiber link 114 that is transmitted to the opticalswitch 142. The optical switch 142 is used to couple an optical signalcoming in on a wavelength of an input fiber link 114 a to the samewavelength in an output fiber link 114 b. If the OXC 106 does not haveany wavelength converters, then the input wavelength, λ₁, is associatedwith the same wavelength, on each hop. If the OXC 106 has wavelengthconverters, a different wavelength on each hop can be used to create anoptical bypass circuit. A multiplexer 144 is used to combine theoutgoing wavelengths onto the output fiber link 114 b.

An OXC 106 can have multiple input fiber links and multiple output fiberlinks. The coupling of input optical signals (on a particular wavelengthon an input fiber) to output optical signals (on a particular wavelengthon an output fiber) is reconfigurable. The ability to reconfigure theconnections through OXCs is one means of establishing the desiredoptical bypass circuits.

FIG. 5 is a schematic diagram of an embodiment of the controller 103.Alternatively, the controller can be distributed in the routers in thenetwork 100. The controller 103 has, at a minimum, a memory 122, anetwork interface 124 for facilitating network communication, and aprocessor or CPU 126. The memory 122 can be a computer readable storagemedium that can store executable procedures, applications, and data. Itcan be any type of memory device (e.g., random access memory, read-onlymemory, etc.), magnetic storage, volatile storage, non-volatile storage,optical storage, DVD, CD, and the like. The memory 122 can also includeone or more external storage devices or remotely located storagedevices. The memory 122 can contain instructions and data as follows:

-   -   an operating system 128;    -   an optical bypass circuit procedure 130;    -   data 132; and    -   other applications and data 136.

Attention now turns to a more detailed description of embodiments of themethodology used to create and allocate optical bypass circuits tooffload transmission traffic from the IP routers.

The methodology described herein identifies and allocates the opticalbypass circuit bandwidth to meet the network's demands. There are twophases to this method. Referring to FIG. 6, in the first phase, eachnode X independently determines the maximum number of optical bypasscircuits, each configured to carry a specified amount of traffic, to asmany destinations (not necessarily final destinations of the traffic),that could possibly originate at X. An optical bypass circuit transportstraffic that originates at node X plus transient traffic that X receivesfrom other nodes. All traffic is considered, such as the trafficoriginating and passing through a node. In the second phase, node X willeliminate an optical bypass circuit found in the first phase if any ofits parent nodes P (according to the network routing tree) found in thefirst phase a necessarily longer optical bypass circuit to the samedestination. This second phase comparison is done (in parallel) at allnetwork nodes.

In Phase 1, control messages are sent from a node X to all its neighbors(its descendents in the routing tree). On each of its output links, Xsends a message with a list of the total traffic flows (e.g.,source-destination “identifiers” and aggregate amounts of traffic) onthat link destined to each other network node—provided the aggregatetraffic exceeds a specified threshold (e.g., the desired loading of eachbypass circuit). When a node Y receives this message, it “splits andforwards” the incoming traffic list to its appropriate output linksaccording to the destination nodes of the traffic flows. At node Y,these filtered sets of traffic-flow information (from X to other nodes)are then sent downstream to the next nodes. This continues until theremaining aggregate traffic (that started with the node X message) to agiven destination node D falls below the specified threshold (i.e.,desired loading of each bypass circuit). This occurs either when thecontrol message reaches the final specified destination D, or at somenode W prior to reaching D. At that point, a message is sent in thereverse direction (i.e., up the network routing tree) to X so that allthe intermediate nodes can configure their optical bypass modules tocreate the bypass circuit to node D or alternatively node W. In Phase 2,described next, the starting node of this bypass circuit to D (oralternatively W) is determined. The starting node will either be X or anancestor of X.

In Phase 2, each node tells each of its descendents the list of fullyutilized bypass circuits that it identified in Phase 1. Then, if anynode learns that any one of its parents was able to establish during thefirst phase a bypass circuit to the same end node, then the descendentnode does not become the start node for the circuit to that end node.There is no need because all that traffic is “subsumed” by a longerbypass circuit (that starts at P or one of P's ancestors). If thedescendent node X during the first phase finds more circuits than itsparent P, then these extra circuits from X will start at X.

After Phase 2, the following result is obtained. For all nodes X, therouter at Y, and nodes Z, if the total amount of traffic (i.e., allsource-destination pairs) on Y router's input link X->Y destined for Yrouter's output link Y->Z exceeds a specified threshold (e.g., thedesired loading of each bypass circuit), then that traffic from X to Zwill bypass the router at Y.

Turning to FIG. 7, the optical bypass circuit procedure 130 has eachnode, N_(i), simultaneously determine a set of optical bypass circuitsthat can be established based on an aggregation of the traffic flowthrough each node, N_(i) (step 152). Each node determines the set ofoptical bypass circuits that could originate at their respective node,each configured to carry a specified amount of traffic. As shown in FIG.8, each node sends out control messages to each of its descendentneighbors (step 158). The control messages contain a traffic listdetailing the source-destination pairs that flow through the node andthe corresponding traffic flow information. The node's routing table isused to determine the node's descendent neighbors. Thesource-destination pairs contain the source and destination identifiers.Each node that receives the control message appropriately splitsinformation in the traffic list and forwards control messages to each ofits descendent neighbors, towards the respective destinations listed inthe traffic list (step 160). A control message will either reach itsrespective final destination node or, alternatively, reach a node atwhich the remaining aggregate traffic, in the traffic list, falls belowthe specified threshold. The specified threshold can be the desiredloading of each bypass circuit, typically a high percentage of awavelength's capacity. The last hop or final destination node will thenrespond to the originating node with a reply message. The reply messagewill update the traffic list with the traffic flow for eachsource-destination pairs (step 162). This identifies the phase onepotential optical bypass circuits to that last hop or final destinationnode.

Referring back to FIG. 7, the originating node, N_(i), then eliminatesfrom its set of optical bypass circuits, those source-destination pairsfrom node N_(i) to a destination node that is already included in theset of optical bypass circuits of a parent node (step 154). As shown inFIG. 8, each node sends control messages to each descendent neighbornode with the sending node's set of optical bypass circuits (step 164).If a receiving node determines that one of its parent's nodes have asource-destination pair that is covered by an optical bypass circuit tothe same destination that is found in the receiving node's set ofoptical bypass circuits, the receiving node drops the optical bypasscircuit from its set of optical bypass circuits (step 166).

Referring back to FIG. 7, the originating node then determines if it hasmore optical bypass circuits than its parent's node. In this case, theoriginating node creates extra optical bypass circuits from itself tocover the same source-destination pairs (step 156).

The technology described herein provides the maximum amount of bypassfor a given traffic matrix, topology, and routing protocol. Below aresome examples of the performance gains for a few simple networktopologies with uniform traffic patterns. These performance results areanalytically derived. The gains are even more substantial as the numberof network nodes, wavelengths (which can be assigned to carry bypasstraffic), and traffic loads are increased.

In a cube topology where there are eight OXC nodes interconnected withthree wavelengths per (directional) edge. Attached to each OXC is an IProuter. In other words, each OXC has three direct wavelength connectionsto each of three other OXCs (for a total of nine output wavelengthchannels to other OXCs). Without any bypass there would only be directconnections between neighboring IP routers (through the OXCs). Then, theaverage number of hops from source IP router to destination IP router is(12/7) and the maximum (normalized) traffic input per node is (7/4);i.e., (7/12) on each of the OXC's output wavelength channels. On eachoutput channel, the other (5/12) is used for transit traffic.Consequently, without any bypass, (5/12)=42% of each router'scapacity/processing is spent on transit traffic.

With the technology described herein, two of the wavelengths (perdirectional edge) are used to establish direct connections between allpairs of IP routers that were originally two hops apart in the cubetopology. (Note: in this example with just three wavelengths, there arenot enough wavelengths to also directly connect IP routers that wereoriginally three hops apart.) Now only 12% of each router'scapacity/processing is spent on transit traffic because the maximum(normalized) traffic input is (7/8) on each of the OXC's outputwavelength channels and only (1/8) is needed to handle transit traffic.In addition, the size of the IP routers is reduced from 9×9 (withoutbypass) to 6×6 (with bypass), not counting its local input/output ports.

Now suppose N OXCs (and their associated IP routers) are interconnectedin a ring topology with W wavelength channels in each direction(clockwise and counter-clockwise). For large N, the maximum totalthroughput is approximately (8 W) and the maximum throughput per node is(8 W/N). Consequently, without any bypass, each IP router is of size 2W×2 W (plus local input/output ports), (8 W/N)/(2 W) (4/N) is themaximum (normalized) input traffic per wavelength channel, and 1−(4/N)is the fraction of each router's capacity/processing spent on transittraffic.

With the technology described herein in the ring topology, the requiredIP router size can be reduced down to just 4×4 (plus local input/outputports). In this configuration, each IP router has direct connections toits two nearest neighbors (clockwise and counter-clockwise on the ring)plus two maximal-length bypass circuits (of length W−1 in eachdirection). In addition, only 1−(2 W/N) of each router'scapacity/processing is spent on transit traffic.

The embodiments of the systems and methods described herein can be usedfor the selection and creation of optical bypass circuits which can beused in network design and capacity provisioning. They can also be usedfor real-time dynamic sharing of circuit capacities (using rapidcircuit-setup control protocols). The methods are applicable for anygiven topology, routing algorithm, and traffic matrix. For every nodeand every one of its input-output link pairs, if there is sufficienttraffic to bypass the node, then that traffic will be part of somebypass circuit. This implies that the circuits are also “maximallength,” which increases the amount of optical bypass circuits in thenetwork. The embodiments of the methods can be implemented by one ormore central nodes or central controllers 103, if it has all thenecessary topological and traffic information. Alternatively, adistributed control of the methods can be implemented whereby theoptical bypass circuits are created by simply passing local controlmessages between the network nodes. In this embodiment, the networknodes do not need to know the complete network topology, routing, ortraffic matrix.

Although there likely are many distinct traffic flows between a sourceand destination node, the method only needs to consider the aggregate ofall such flows (i.e., “how much” traffic there is on each network link).In the methodology described herein, the optical bypass circuits areshared by all the traffic from a source to destination node. Consideringthe aggregate traffic simplifies the method and maximizes the amount oftraffic that is offloaded by the optical bypass circuits. Also, when theoptical bypass circuits are created, there is no change in the “physicalroute” of the packets from source to destination; at some nodes, thereis only a change in some hops through the IP routers to the OXCs. Thishelps reduce the end-to-end delay jitter (because propagation delaysdominate in these high-speed networks) in situations where mid-callcutover is enabled and permitted to/from the optical bypass circuitswhenever there is sufficient traffic. This helps in scenarios where theaggregate traffic from a source to a destination node is split so thatonly a portion goes through the created optical bypass circuits.

Since packets sent over end-to-end optical bypass circuits/wavelengthsare assumed to not suffer packet loss, another important advantagegained by the use of the optical bypass is a reduction in the overallnetwork packet loss probability. Further reduction is possible if theload on the remaining packet wavelengths is reduced. This is due to thefact that the effective loading can be higher on the end-to-end opticalbypass circuits than on the point-to-point wavelengths between TProuters, due to contention and buffering. This load reduction on therouters is particularly beneficial when deploying ODRs in the networksince they currently are of small size and have very limited opticalbuffering capabilities (e.g., only tens of short optical cells). Theperformance gains depend on the number of wavelengths per fiber (moregenerally, the number of bypass channels at each node). In the limit, ifthe number of wavelengths is extremely large, it would be possible tocreate a fully connected logical topology of only optical bypasscircuits.

The foregoing description, for purposes of explanation, has beendescribed with reference to specific embodiments. However, theillustrative teachings above are not intended to be exhaustive or tolimit the invention to the precise forms disclosed. Many modificationsand variations are possible in view of the above teachings. Theembodiments were chosen and described in order to best explain theprinciples of the invention and its practical applications, to therebyenable others skilled in the art to best utilize the invention andvarious embodiments with various modifications as are suited to theparticular use contemplated.

The methodologies described herein can be used to bypass other networkcomponents other than IP routers, such as optical data routers.Furthermore, the optical bypass circuit procedure can be repeatedmultiple times where at each iteration, there are decreasing bandwidthallocations to create a multi-layer hierarchy of different rate bypasscircuits in the network. In addition, the methodology described hereincan also be utilized for any type of bypass circuits and is not limitedto just optical bypass circuits.

1. A method for generating bypass circuits in a network, comprising:associating a plurality of nodes with the network, each node havingtraffic from one or more source-destination pairs and associated with atraffic list for each source-destination pair; calculating an aggregatetraffic flow, for each node in the network, for all thesource-destination pairs flowing through the node; and determining a setof bypass circuits, for each node in the network, based on theaggregated traffic flow, each bypass circuit is associated with a selectsource node and a select destination node, wherein the select sourcenode and the select destination node need not be a source-destinationpair.
 2. The method of claim 1, further comprising: for each node,eliminating from the node's set of bypass circuits, bypass circuitsincluded in a parent node's set of bypass circuits.
 3. The method ofclaim 1, wherein the calculating step further comprising: transmittingcontrol messages to each descendent node, the control messages includinga traffic list; and updating the traffic list with local traffic flowinformation, by each node receiving the transmitted control message. 4.The method of claim 3, further comprising: reaching a destination node;and generating a bypass circuit that reaches the destination node. 5.The method of claim 2, wherein the eliminating step further comprising:for each node, transmitting the node's set of bypass circuits to eachdescendent node.
 6. The method of claim 1, wherein the determining stepfurther comprising: creating additional bypass circuits not contained ina parent node's set of bypass circuits.
 7. The method of claim 1,wherein the bypass circuit is generated to accommodate a traffic flowcapacity of one wavelength.
 8. The method of claim 1, wherein the bypasscircuit is an optical bypass circuit.
 9. A system for allocating bypasscircuits in a network, comprising: a plurality of nodes, each nodehaving traffic from one or more source-destination pairs; one or morebypass circuits, each bypass circuit associated with a select sourcenode and a select destination node; and a bypass procedure thatgenerates one or more bypass circuits, the bypass procedure havinginstructions to have one or more nodes in the network calculate anaggregate traffic flow for all source-destination pairs flowing througheach node; and create one or more bypass circuits based on theaggregated traffic flows through the nodes.
 10. The system of claim 9,wherein the bypass procedure further includes instructions to calculatethe aggregate traffic flow by having each node in the network transmitcontrol messages to each descendent node for each source-destinationpair flowing through the node, the control message including anaggregated traffic flow that each descendent node updates with its localtraffic flow.
 11. The system of claim 10, wherein the bypass procedurefurther includes instructions to have a destination node receiving thecontrol message respond to the node originating the control message withthe aggregated traffic flows.
 12. The system of claim 11, wherein thebypass procedure further includes instructions to have the originatingnode create a bypass circuit based on the received aggregated trafficflow.
 13. The system of claim 9, wherein the bypass procedure furtherincludes instructions to have a node delete bypass circuits alreadycovered by a bypass circuit created by a parent node.
 14. The system ofclaim 9, wherein the bypass circuit is generated to accommodate atraffic flow capacity of one wavelength.
 15. The system of claim 9,wherein the select source node and the select destination node of abypass circuit includes an optical cross connect.
 16. The system ofclaim 9, wherein the bypass circuits are optical bypass circuits.
 17. Acomputer program product having a computer readable storage mediumcomprising: a routing table including one or more source-destinationpairs used to route data through a network, the network having aplurality of nodes; a traffic matrix having traffic flow data for eachsource-destination pair flowing through a node; a bypass procedure thatgenerates one or more bypass circuits, each bypass circuit associatedwith a select source node and a select destination node, the bypassprocedure having instructions to calculate an aggregate traffic flow forall source-destination pairs flowing through the node; and create one ormore bypass circuits based on the aggregated traffic flow through thenode.
 18. The computer readable storage medium of claim 17, wherein thebypass procedure further includes instructions to calculate theaggregate traffic flow by having each node in the network transmitcontrol messages to each descendent node for each source-destinationpair flowing through the node, the control message including anaggregated traffic flow that each descendent node updates with its localtraffic flow.
 19. The computer readable storage medium of claim 17,wherein the bypass procedure further includes instructions to have anode delete a bypass circuit that is already contained in a bypasscircuit created by a parent node.
 20. The computer readable storagemedium of claim 17, wherein the bypass circuits are generated toaccommodate a traffic flow capacity of one wavelength.